The use of medicament dispensers in the delivery of medicaments to the lung is well known. Such dispensers generally comprise a body or housing within which a medicament carrier is located. Known inhalation devices include those in which the medicament carrier is in blister pack form (e.g. an elongate blister strip) containing a number of discrete doses of powdered medicament. In use, the blister pack is typically housed within the dispenser in such a way that the blisters may be transported through the dispenser in indexed fashion to enable accessing of the discrete doses of medicament carried thereby. Such devices usually contain a mechanism of individually accessing the doses contained within the blisters. Known access mechanisms typically comprise either blister piercing means or means to peel a lid sheet away from a base sheet of the blister pack. The powdered medicament can then be accessed and inhaled.
It is desirable that elongate blister strip form medicament carriers for containing medicament in dry powder form have suitable moisture transfer properties. Whilst to an extent, the optimal character of such properties is dependent on the nature of the particular medicament formulation to be carried within the blister it is generally beneficial for the material of the strip and of any seals made thereto to either prevent or at least to significantly slow down moisture ingress to the medicament contained within the blister to prevent the moisture-induced degradation or agglomeration thereof. Reducing moisture permeation reduction to the cavity of the blister pack and thereby enhancing the stability of the medicament contained therein are particular targets of interest. Efforts therefore continue to be expended in the development of improved strip materials, pack forms and sealing methods.
Conventional high barrier medicament blister packs typically comprise aluminium foil sheets in both the lid sheet and base sheet components thereof. The aluminium sheets are selected to have sufficient thickness to be substantially free of ‘pinhole’ imperfections thereby making them essentially impermeable to the transfer of moisture. In developments thereof, laminate form sheets are used for either one or both of the lid and base sheets, which laminates typically comprise a layer of aluminium foil and one or more polymeric layers. Such laminates are typically employed when a ‘cold form’ method is employed to form the base sheet with blister pockets. Polyvinyl chloride (PVC) is conventionally used as the material of the polymeric layer.
The Applicants have now appreciated that such polymeric layers act as the principal conduit for moisture ingress to the medicament contained within the blisters. The absolute rate of flow of moisture is dependent on various factors including prevailing environmental conditions, the polymer material and properties of the medicament itself (e.g. hygroscopic or desiccant properties).
The Applicants have now found that moisture ingress to the interior of the blister may be reduced by the selection of particular, unconventional polymeric materials for use in the laminate sheets of the blister packs. The Applicants have also found that moisture ingress may also be reduced by the use of polymeric layers in the laminates, which have reduced thickness compared to conventional polymeric layers. Enhancements in the storage stability of dry powder form medicament contained within the blister packs may thereby be achieved.
The Applicants have further found that certain of the new polymeric materials can act to provide an enhanced oxygen barrier. That is to say, the layer comprising the new polymeric material acts such as to reduce oxygen permeation, and thereby also reduce oxygen ingress to the medicament contained within the blister. This can be important where the medicament is susceptible to oxidative degradation,
The Applicants have also further found that certain of the new polymeric materials can act to modify the static electricity-related properties of the laminates and blister pack. This can be important where the powder form medicament is susceptible to adhere to the interior of a blister cavity because of static electricity effects thereby affecting the ability to release/deliver the powder from an opened blister pack.